The invention relates to remote controls and, more particularly, to universal remote controls for use with consumer electronic products.
Consumer electronic devices commonly are controlled by a remote control. A consumer may have a separate remote control for a television, a stereo, a video cassette recorder, or other such device. The convenience of remotely controlling these devices is reduced by having to locate a specific remote for a specific device or carrying around several remote controls. It is preferable to have a single remote control for controlling each of the several devices.
Two types of universal remote controls which are currently in the marketplace for consolidating several remote controls into a single remote control unit are preprogrammed and learning. Since each manufacturer uses a different bit pattern for carrying out a specific operation and uses a different method of transmitting the pattern, the preprogrammed remote control has a large data base of codes, devoting a large part of its internal memory to the storage of these codes. Each consumer chooses only a few codes to see if those codes will control their consumer electronic devices. To save on the cost of parts of the preprogrammed remote control, some codes will be left out of the data base, making the resulting product useful to a subset of potential customers.
A learning type of remote control is disclosed in U.S. Pat. No. 4,623,887 issued Nov. 18, 1986 to Welles, II and entitled "Reconfigurable Remote Control" and in U.S. Pat. No. 4,626,848 issued Dec. 2, 1986 to Ehlers and entitled "Programmable Functions for Reconfigurable Remote Control". The infrared codes of each remote control are transmitted into the universal remote control, which learns or memorizes the codes. The data is compressed and stored for later use.
However, learning remote controls cannot learn all infrared codes. Learning remote controls typically concentrate on the carrier and inter-carrier pauses, missing other information crucial to an accurate representation of a true signal. For example, several manufacturers send data at the beginning or the end of a transmission that is different than the data throughout the middle of the transmission. Others send different data each time the same key is pressed, or send multiple carriers in one transmission that is difficult to detect by a sampling and averaging method of the learning remote control.
U.S. Pat. No. 5,194,978 issued to Heep on Mar. 16, 1993 and entitled "Timer System for Learning and Replaying of Infrared Signals" discloses a timer method used to learn an infrared transmission from a native remote control. The remote controller determines which of four modes of transmission a signal is transmitted in, including carrier mode, pulse mode, frequency shift keying mode and continuous wave mode. Once the device knows the transmission method, it can set its internal timers to detect the infrared pulses and pauses between the pulses for detecting the data.
However, the transmission method is only a part of the information contained in the bit modulation technique, which is a part of a Protocol. For example, the carrier mode of transmission can be employed to create several bit modulation schemes or techniques. The bit modulation technique is one parameter of the Protocol. By detecting only a portion of the Protocol, the problem of overall recognition of the complete signal is not solved. Also, the device does not solve the problem of memory storage space due to the necessity of storing timing information in addition to other relevant information.
Therefore, what is needed is an apparatus and method for remotely controlling consumer electronic devices which utilizes a comparative approach of identifying a transmission technique and using that technique to detect and store the specific infrared code for later re-transmission.